Impact apparatus



Nov. 14, 1967 c, BOLLAR 3,352,143

IMPACT APPARATUS Filed April 2 1965 2 Sheets-Sheet l lsa 62 (639414193 L. C. BOLLAR Nov. 14, 1967 I MPAOT APPARATUS 2 Sheets-Sheet 2 Filed April 1965 United States Patent 3,352,143 WACT APPARATUS Leo C. Bollar 5942 Erlanger St., San Diego, Calif. 92122 Filed Apr. 2, 1965, Ser. No. 444,994 Claims. ((31. 72-445) ABSTRACT OF THE DESCLDSURE A ram for delivering impact force is slidingly embraced by an annular piston which is a movable partition between an upper liquid filled compartment and a lower compartment filled with compressed air, the working end of the ram extending through the lower compartment into the atmosphere. Normally the upper end of the ram is held by fluid pressure in an upper low pressure seat that is vented to the atmosphere. Raising the pressure in the seat reverses the pressure differential on the ram to start the downstroke. During the first part of the stroke the compressed air expands to drive the ram downward with consequent upward shift of the annular piston until the upwardly moving annular piston meets an annular shoulder of the downwardly moving ram. During the second part of the stroke the ram carries the annular piston downward to compress the air in the lower compartment thereby to decelerate the ram.

This invention relates to an impact apparatus which may be adapted to impact forming of workpieces or may be adapted to deliver impact force for other purposes such as pile driving, demolition and the like. Certain features disclosed herein are also disclosed in my copending application entitled, Impact Forming Machine, Ser. No. 279,055, filed May 9, 1963, now Patent No. 3,267,677, and in my copending application entitled, Impact Forming Apparatus, Ser. No. 328,787, filed Dec. 2, 1963, now Patent No. 3,205,790.

An impact apparatus of the type to which the invention pertains comprises essentially a structure forming a rearward chamber to contain fluid under pressure, a guide passage extending forward from the chamber, and a ram slidingly mounted in the guide passage for actuation by the fluid. More specifically, the invention pertains to such an apparatus in which the rear end of the ram is backed into a cooperating sealing seat when the apparatus is eady for a working stroke, the sealing seat serving to isolate the rear end of the ram from the high pressure fluid to keep the ram retracted until the working stroke is desired.

The sealing seat is normally vented to a low pressure region to keep the pressure low at the rear end of the ram and the working stroke may be initiated with a time delay by simply cutting off the vent passage until leakage into the sealing seat raises the pressure therein to an effective magnitude. Such a time delay may be avoided by simply forcing fluid abruptly into the seat as soon as the vent passage is cutoff.

Gaseous fluid is required in the chamber for expansion to drive the ram but it is highly desirable to employ a liquid fluid in the region of the sealing seat to facilitate control of leakage into the seat. Accordingly, a movable wall such as a floating piston is provided in the chamber to divide the chamber into a first compartment containing a body of gaseous fluid and a second compartment containing a body of liquid fluid, the floating piston separating the two bodies of fluid and serving to transmit actuating pressure from the body of gaseous fluid to the body of liquid. When the rear end of the ram is unseated to initiate a Working stroke, the gaseous body expands to actuate the ram by pressing the movable piston against the liquid body that encloses the rear end of the ram.

One of the important objects of the present invention is to increase the maximum number of operating cycles or working strokes of the piston that may be carried out in a unit of time. The initial embodiment of the invention is capable of delivering high energy impact strokes of the ram repeatedly at a frequency of fifteen times a minute, only one second being required for a complete operating cycle including the resetting of the ram. As will be apparent from the disclosure, this object is accomplished by a new organization of the working parts which shortens the time required to reset the apparatus for an operating stroke.

In the usual apparatus of this character constructed for impact forming of workpieces, the ram is decelerated by means outside of the working mechanism. Thus the ram is decelerated by transferring energy to a workpiece or to a platen or anvil in the absence of a workpiece. Such an apparatus cannot be used safely for purposes such as demolition because if the ram misses the mark or encounters too little resistance the ram becomes a hazard. A further important object of the present invention, therefore, is to provide a ram action that is self-limiting in that the stroke of the ram is divided into an initial range of energy input into the ram and a final range of deceleration in which energy is stored for immediate automatic retraction of the ram.'Thus if the ram is not completely decelerated by encountering external resistance, the ram is automatically decelerated and retracted.

This last object is achieved by a number of provisions which work together. One provision is that the floating piston that divides the chamber into two compartments is in the form of an annular piston that slidingly embraces the ram. A second provision is that the gaseous body for driving the ram is in the forward compartment and the liquid which acts directly on the ram is in the rearward compartment. This arrangement is the reverse of an arrangement that'has been employed heretofore and results in the floating piston retracting rearwardly. instead of advancing, as energy is transmitted to the forwardly moving ram. The third provision is means for engaging the advancing ram with the retracting floating piston to terminate the initial portion of the stroke in which energy is transmitted to the ram. Thereafter, the floating piston is advanced by the advancing ram during the final portion of the stroke of the ram.

The fourth provision is designing the forward compartment for contraction in volume by the floating piston when the floating piston is advanced by the ram during the final portion of the stroke of the ram. Thus during the final portion of the stroke of the ram the gaseous fluid in the forward compartment is compressed by the advancing floating piston to decelerate the ram and to store energy for subsequent return of the ram.

A feature of the preferred practice of the invention is the further provision of dashpot means to cushion the impact of the advancing ram against the retracting floating piston. Another provision in the preferred practice of the invention is means to cushion the automatic return movement of the ram to avoid damage to the apparatus.

In an impact forming apparatus of this type as heretofore constructed, it is often difficult to release a forming die from a formed workpiece. The present invention eliminates this difficulty by providing a body of compressed gaseous fluid to tend to retract the forming die from an advanced position and by further providing releasable holding means to block retraction of the forming die from its advanced position by the compressed gaseous fluid. After a part is formed by the dies the holding means is operated to release the forming die for retraction and subsequentlymeans is employed to restore the forming die to its normal advanced position in opposition to the pressure of the gaseous fluid.

The various features and advantages of the invention may be understood from the following detailed description together with the accompanying drawings.

In the drawings, which are to be regarded as merely illustrative:

FIG. 1 is a diagrammatic sectional view of the presently preferred embodiment of the invention;

FIG. 2 is a simplified diagrammatic view showing the position of theworking parts when the apparatus is set or ready for a Work stroke;

FIG. 3 is a view similar to FIG. 2 showing how the apparatus is triggered by unseating the head of the ram to initiate a work stroke;

FIG. 4 is a similar view showing the ram head seated against the floating piston at the end of the initial energy-input portion of the stroke of the ram; and

FIG. 5 is a similar view showing the ram at the end of its stroke.

FIG. 1, illustrating the presently preferred embodiment of the invention for the impact forming of parts, shows a fluid-confining structure comprising a main cylinder closed at its upper end by a head casting 12, and an inner cylinder 14 which is telescoped into the main cylinder and is sealed by an O-ring 15. The main cylinder 10 is mounted in a fluid-tight manner on a large block of metal 16 which in turn is mounted on a base structure 18. A lower cylinder 26 in the form of a liner sealed by an O-ring 22 is mounted in the block 16 in axial alignment with the main cylinder 10, the liner being removably secured by a split collar 24. The main cylinder 10 forms a fluid-confining chamber and the inner cylinder 14 forms a guide passage that extends downward from the chamber and is of smaller diameter than the chamber.

A ram, generally designated'25, which extends into the fluid-confining chamber for actuation by fluid pressure therein has a body or main portion 26 that is slidingly mounted in the guide passage provided by the inner cylinder 14, the ram carrying an O-ring 28. The ram is further formed with a long neck or shank 30 of uniform diameter and an enlargement or head 32 is retained on the upper end of the neck by a welded collar 34.

Slidingly embracing the neck 39 of the ram 25 in a freely movable manner is a movable wall in the form of an annular piston 35 that is preferably of light weight and may be made of aluminum. The annular piston is provided with an inner O-ring 36 for sealing contact with the neck 30 and is further provided with an outer O-ring 38 for sealing contact with the surrounding main cylinder 10. The annular piston 35 in cooperation with the neck 39 of the ram divides the fluid-confining chamber into a forward or lower compartment 40 which contains a body of gaseous fluid such as air and a rearward or upper compartment 42 (FIG. 2) which contains a body of liquid fluid such as a suitable grade of oil.

The head casting or cylinder head 12 forms a seat 44 for the ram head 32 which seat serves to isolate the rearward surface of the ram head from the high pressure of the body of liquid in the upper compartment 42. It is to be noted that the seat 44 has a cylindrical entrance 45 of appreciable axial dimension and that the ram head 32 has a corresponding peripheral cylindrical surface of appreciable axial extent. Normally the seat 44 is placed in communication with a low pressure zone by a vent passage 46 which communicates with an external pipe 48.

As shown diagrammatically in FIG. 1, the pipe 48 communicates through a normally open solenoid valve 50 with a reservoir or tank 52 and the pipe 43 is also connected through a check valve 54 with a power actuated pump 55 for withdrawing liquid from the reservoir. When the ram head 32 is in the seat 44, as shown in FIG. 2, leakage occurs at a slow rate from the pressurized oil in the upper compartment 42 but as long as the passage 45 is in communication with the low pressure zone at the reservoir 52, pressure cannot build up in the seat. The fact that the seat has the cylindrical entrance 45 for cooperation with the cylindrical portion of the ram head 32 isa safety feature because the ram head must be retractcd an appreciable distance from its fully seated position to make the rear surface of the ram head accessible to the high pressure oil.

A second passage 56 in the cylinder head 12 places the upper compartment 42 in communication with a suitable source of high pressure oil. As shown diagrammatically in FIG. 1, passage 55 is connected to a pipe 53 through a suitable power-actuated pump 62 which draws liquid from the reservoir 52. The pipe 58 may be placed in direct communication with the low pressure reservoir 52 by opening a normally closed solenoid valve 64.

As may be seen in FIG. 1, the lower side of the ram head 32 is of convex configuration and the upper side of the floating piston 35 is of corresponding concave configuration to form a seat for. the ram head. The significance of this relationship is that when the ram head and the annular piston are abruptly moved together a certain dashpot effect cushions the impact.

For impact forming of a part or workpiece, a stationary lower die 65 mounted on a platen 66 cooperates with an upper die 68 which is attached to a normally stationary metal body 70 which serves to transmit energy from the ram 25 to the upper die. The metal body 70 is slidingly mounted in the lower cylinder 20 and for this purpose is formed with an enlargement or head 72 that is equipped with a suitable O-ring 74.

The lower end of the metal body 70 is guided by an annular sealing ring 75 which cooperates with the head 72 to form a variable annular chamber 76 which contracts when the metal body 70 is moved downward by the force of the ram 25. This annular chamber 76 is filled with compressed gaseous fluid such as air to serve as resilient means for retracting the metal body after a working stroke thereby to free the upper die 68 from the formed part.

In preparation for a working stroke, the upper die 68 is held at a normal advanced position in contact with the workpiece by suitable hydraulic means in opposition to the pressure of the gaseous fluid in the annular chamber 76. For this purpose, a pressure ring 78 engages the upper die 68 from above and is held down by a pair of hydraulic rams 80. After an impact stroke has been delivered to form a workpiew, the two hydraulic rams 80 are retracted to permit the gaseous fluid in the annular chamber 76 to retract the upper die 68 from the workpiece so that the formed workpiece can be removed. When a new workpiece is in position for a forming operation the two hydraulic means are advanced to restore the upper die to its normal advanced position. The pressure of the gaseous fluid in the annular chamber 76 may vary between p.s.i. and 2,000 p.s.i. depending upon the character of the workpiece and the degree to which the workpiece is deformed by the impact.

The space between the ram 25 and the metal body 70 constitutes a lower chamber which is contracted as the ram moves toward the metal body. A small body of oil 32 is provided at the bottom of this lower chamber to serve as means for transmitting the energy of the ram to the metal body 70. It is to be noted that the circumferential wall 84 surrounding the body of oil 82 .is dimensioned for relatively snug fit with the ram 25 so that the body of oil is effectively trapped as the ram approaches the lower metal body 70 and it is to be further noted that the diameter of the head 72 of the metal body 70 is of substantially larger diameter than the circumferential wall 84. Thus the area of the lower body 70 that is exposed to the pressure of the oil 82. is desirably greater than the cross-sectional area of the ram 25.

The space in the lower chamber above the oil body 82 is occupied by air at low pressure and it is desirable to provide a space into which the air may be displaced by the working stroke of the ram. For this purpose the inner cylinder 14 cooperates with the main cylinder to form an annular chamber 85. Communication with the annular chamber 85 is provided by a passage 86 which is close to the level of the body of oil 82. Thus when the ram 25 makes a working stroke the air between the advancing ram and the body of oil 82 may be displaced through the passage 86 into the annular chamber 85.

As will be explained the high pressure gaseous fluid in the lower compartment 40 causes the ram 25 to be returned upward at high velocity after a working stroke. In some installations of the device it may be desirable to make some provision for preventing the creation of a destructive pressure rise in the upper compartment 42 when the ram is returned at high velocity when both of the valves 51 and 64 are closed to prevent escape of the hydraulic fluid. For this purpose an auxiliary piston 88 provided with an O-ring 90 may be mounted in an auxiliary cylinder 92 that communicates with the seat 44 in the upper end of the upper compartment 42.

The auxiliary piston 38 is formed with a circumferential shoulder 54 which normally seats against a corresponding shoulder 95 of the auxiliary cylinder, the auxiliary piston being urged to this position by pressurized gaseous fluid in the auxiliary cylinder. A feature of the invention in this regard is that the auxiliary cylinder 92 is in continuous communication with the lower compartment 40 through a suitable pipe 96 to maintain the desired pressure in the auxiliary cylinder.

Operation FIG. 2 shows the apparatus ready for a working stroke with the ram head 32 in the seat 44 and with the annular piston 35 spaced a substantial distance below the ram head. As shown in FIG. 1, the holding means in the form of the two hydraulic rams 80 holds the upper die at its normal advanced position with the body 70 at a corresponding advanced position in opposition to the gaseous pressure in the annular chamber 76. It is apparent that while the two hydraulic rams 80 block retraction of the upper die 68 from its normal advanced position, the upper die is free to advance towards the lower die 65 to carry out the forming operation on a workpiece. The gaseous fluid in the lower compartment 40 is under high pressure and this pressure is transmitted to the oil in the upper compartment 42 by the annular piston 35. Oil continually leaks at a slow rate from the compartment 42 past the ram head 32 into the seat 44 but the pressure of the oil in the seat 44 is low because the vent passage 46 is open to a low pressure region.

The ram head 32 may unseated with a time delay by simply cutting oif the vent passage 46 so that the leakage of the oil into the seat 44 eventually builds up the pressure in the seat. In the preferred practice of the invention, however, the time delay is avoided by operating the pump 55 (FIG. 1) in addition to closing the solenoid valve 50. The pump delivers oil into the seat 44 to force the ram head 32 downward. As soon as the ram head 32 clears the seat 44 as shown in FIG. 3, the highly pressured oil in the upper compartment 42 has free access to the rear surface of the ram head 32.

With the pressure of the oil in the upper compartment 42 acting on the rear face of the ram head 32 and with the pressure of the gaseous fluid in the lower compartment 40 acting on the annular surface 98 of the body of the ram, the ram is accelerated downwardly at a high rate. As a progressively increasing proportion of the ram enters the lower compartment 40 from the upper compartment 42, the resultant change in displacement results in corresponding upward retraction of the annular piston 35.

As the ram head 32 approaches the annular piston 35 and makes impact therewith as shown in FIG. 4, the

previously mentioned dashpot action occurs to cushion the impact. Up to this point the gaseous fluid in the lower compartment 40 expands to deliver energy to the ram 25. Beyond this point of impact of the ram head against the annular piston no further energy is delivered to the ram. On the contrary, beyond this point the downward movement of the annular piston by the ram head contracts the volume of the lower compartment 40 to store energy by compressing the gaseous fluid therein.

When the ram at its lowest point shown in FIG. 5 is completely decelerated by impact against the lower oil body 82 and the consequent transfer of energy to the upper die 68, the ram is promptly returned upward primarily by expansion of the gaseous fluid in the lower compar-tment 40. The downward movement of the ram displaces air into the annular chamber 85 with consequent compression of the air and re-expansion of this compressed air further assists to a minor degree to return the ram. It is also to be noted that the downward movement of the ram after the ram head makes contact with the annular piston, creates a void in the upper compartment 42 Y which also facilitates upward return of the ram.

It is apparent that the working stroke of the ram is divided into two parts or ranges and the return stroke of the ram is also divided into two parts or ranges. Thus on the working stroke of the ram, the first portion of the stroke terminates when the ram head makes contact with the annular piston and on the return stroke of the ram the first portion of the return stroke terminates when the annular piston separates from the ram head upon impact of the annular piston against the oil body in the upper compartment 42.

When the returning ram and annular piston make impact against the oil body in the upper compartment 42 the resultant abrupt pressure rise causes the auxiliary piston 88 to retract in the auxiliary cylinder 92 to limit the pressure rise and to provide time for the disengagement of the annular piston from the ram head. As the ram head 32 continues to move upward away from the annular piston into the oil body in the upper compartment 42, the volume of the lower compartment 40 is rapidly contracted both by the upward movement of the ram body 26 and by the downward movement of the annular piston that is caused by displacement of oil in the upper compartment 42. As a consequence the ram is rapidly decelerated to terminate its return movement.

It is apparent that there is some tendency for the ram to oscillate but the oscillation is of brief duration and is not troublesome. At the end of the oscillation the parts come to rest at the positions shown in FIG. 4 with the ram head 32 sea-ted against the annular piston 35.

To reset the apparatus in preparation for a new working stroke, oil is released from the upper compartment 42 and this step may be carried out quickly by opening both valves 50 and 64 to permit the oil to escape rapidly through the passages 46 and 56 in the cylinder head. As the oil escapes from the upper compartment 42, the gaseous fluid in the lower compartment 40 expands to lift the annular piston 35 and thereby lift the ram head 32 into the seat 44. When the ram head is fully seated the parts are positioned as shown in FIG. 1.

As soon as the main ram 25 starts to rise, the two hydraulic rams are retracted to permit the gaseous pressure in the chamber 76 to lift the upper die 68 to a retracted position to permit the formed workpiece to be removed from the dies. A new workpiece is then placed in the lower die 65 and the hydraulic rams 80 are again operated to restore the upper die 68 to its normal advanced position.

The second step to reset the apparatus for a new working stroke is to close the valve 64 (FIG. 1) and to start the pump 62 to return oil to the upper compartment 42 in opposition to the pressure of the gaseous fluid in the lower compartment 40. As new oil is pumped into the upper compartment 42, the annular piston is correspond- 7 ingly advanced downward away from the seated ram head 32.

Introduction of new oil is terminated when the downward movement of the annular piston 35 raises the pressure of the gaseous fluid into the lower. compartment 40 to a desired magnitude which depends upon how much energy is required for a particular workpiece. Thus the annular piston may be restored to the starting position shown in FIG. 2.

It is apparent that maximum energy may be stored for application to a workpiece by advancing the annual piston to the maximum where the piston abuts the upper end of the inner cylinder 14. The operator determines how much oil is to be returned to the upper compartment 42 by watching the pressure in the lower compartment 40 as registered by a gauge 99 (FIG. 1) in a pipe 160 that communicates with the lower compartment. The pipe 100 is normally closed by a valve 101 which may be opened whenever desired either to release gaseous fluid from the lower compartment or to permit gaseous fluid to be introduced by a power actuated pump 102. In shifting from the forming of one workpiece to the forming of a diflerent workpiece, it is ordinarily not necessary to increase or decrease the amount of gaseous fluid in the lower compartment.

If the apparatus is to be employed for impact purposes other than impact forming, for example if the apparatus is to be employed for demolition or for pile driving or the like, only the structure above the block 16 is required, i.e., only the structure that is associated with the main cylinder 10. The open end of the main cylinder is presented to whatever object is to be struck by the leading face of the ram 25. The compression of the gaseous fluid in the lower compartment 40 by the operating stroke of the ram now has special importance because it limits the degree to which the ram is advanced on the operating stroke without regard to external resistance encountered by the ram. Thus if the ram encounters no obstacle whatsoever the ram will simply decelerate and retract after making an operating stroke.

Dimensional relationships Certain dimensional relationships are to be noted for a complete understanding of the invention. A feature of the preferred practice of the invention is that the ram head 32 is of slightly larger diameter than the body 26 of'the ram. Thus the area of the annular surface on the underside of the ram head 32 is slightly larger than the annular surface 98 of the ram body 26. The advantage of this relationship is that once the ram head 32 is in the seat 44 a pressure differential exists which continuously urges the ram head into its seat. This pressure differential together with the fact that the ram head must advance appreciably to open the seat is important for safe operation of the device and insures that the working stroke will not be triggered by vibration of the apparatus by external causes.

Another dimensional relationship is that the inside diameter of the main cylinder 10 must be sufficiently larger than the diameter of the ram head 32 to permit the ram head to move freely on its working stroke, i.e., to permit free displacement of the oil around the periphery of the advancing ram head. For this purpose, the area of the annular clearance around the ram head 32 may be approximately half of the area of the ram head.

It is not essential in all practices of the invention that the gaseous fluid in the lower compartment 40 be compressed during the latter part of the operating stroke but the advantages of such compression are of great importance. In this regard it is to be notedthat the inside diameter of the main cylinder 10 must be substantially larger than the inside diameter of the inner cylinder 14. In other words the diameter of the annular piston 35 must be greater than the diameter of the body 26 of the ram if the downward movement of the annular piston is to have the effect of recompressing the gaseous fluid in the lower compartment 40.

Another dimension to be considered is the diameter of the uniform neck 30 of the ram. The diameter must be substantial but the greater the diameter the greater the rate at which the annular piston 35. moves upward to meet the ram head 32 during the initial portion of the Working stroke of the ram. The length of the neck 30 of the ram is also important. The range of movement of the annular piston from its uppermost position shown in FIG. 1 to a lowermost limit position against the end of the inner cylinder 14 must be greater than the distance in FIG. 1 from the lower face of the ram body 26 to the surface of the lower oil body 82. With such a relationship the annular piston cannot interfere with the working stroke of the ram.

Finally, the cross-sectional area of the passage 86 that communicates with the annular chamber should be on the order of one-tenth of the cross-sectional area of the body 26 of the ram. If the cross-sectional area of the passage 36 is substantially less than one-tenth of the area of the ram the freedom for flow of air into the annular chamber 85 will be unduly restricted. On the other hand, if the cross-sectional area of the passage 86 is substantially more than one-tenth of the area of the ram 21 substantial quantity of the oil 82 will pass through the passage into the annular chamber 85. With the cross-sectional area of the passage 86 approximately one-tenth of the area of the ram the passage has a certain selective efiect in that it permits the free flow of air but, in effect, substantially blocks the flo'w of oil.

Automatic high energy cycling Automatic recycling may be accomplished by arranging for the advance of the annular piston 35 to unseat the ram and thereby trigger a working stroke. By way of example, FIG. 1 shows a shoulderlZO on the neck 30 of the ram positioned for abutment by the annular piston 35 as the annular piston advances in response to the introduction of oil through the passage 56. When oil continues to be introduced through passage 56 after the advancing annular piston 35 makes contact with the shoulder 120, the annular piston advances. the ram and thereby withdraws the ram head 32 from the seat 44 to give the highly pressurized oil access to the rear face of the ram head.

As the working stroke is carried out, the annular piston 35 retracts in the manner heretofore described until it comes into abutment with the ram head 32 and then the annular piston is advanced with the ram to complete the working stroke in opposition to the rising of pressure of the gaseous fluid in the lower compartment 40. After the operating stroke is completed, the pressure of the gaseous fluid in the lower compartment 40 acting on the annular piston 35 returns the ram to its initial position with the ram head 32 in the seat 44.

To make such automatic recycling possible, the solenoid valve 50 is continuously open, the vent passage 46 is of large flow capacity and the pump 62 is run continuously with the solenoid valve 64 continuously closed. With the vent passage 46 of large flow capacity, oil flows with sufficient freedom through the vent passage to permit the annular piston 35 to return the ram head 32 quickly to its seat under the pressure of the gaseous fluid in the lower compartment 40. It is apparent that the flow capacity of the vent passage 46 must take into account that oil is being continuously pumped into the upper compartment through the passage 56. As soon as the ram head 32 is seated to cut off the vent passage 46, the oil pumped into the upper compartment through the passage 56 causes the annular piston 35 to advance into contact with the shoulder to initiate a new operating cycle.

Since the amount of energy that is delivered on a working stroke depends on how far the annular piston is advanced before the working stroke is initiated, it is apparent that the advanced position of the shoulder 120 in FIG. 1 results in a high energy output on each working stroke when the apparatus is recycling automatically. If a lower energy output is desired with automatic recycling, a spacer sleeve may be mounted on the neck 30 in abutment with the shoulder 120 to cause the ram to be unseated at an earlier point in the advance of the annular piston 35.

My description in specific detail of the presently preferred embodiment of the invention will suggest various changes, substitutions and other departures from my disclosure within the spirit and scope of the appended claims.

I claim:

1. In an impact apparatus, the combination of:

a structure forming a rearward chamber with a guide passage extending forward therefrom;

an impact ram having a forward impact portion slidingly mounted in the guide passage and a rearward portion extending into the rearward chamber, said rearward portion being of smaller cross-sectional area than the rearward chamber;

an annular piston slidingly mounted in the rearward chamber and slidingly embracing the ram to co operate therewith to divide the chamber into a rearward compartment and a forward compartment;

a rearward body of liquid fluid in the rearward compartment to act on the rear end of the ram to drive the ram;

a forward body of compressed gaseous fluid in the forward compartment,

the annular piston being freely movable for transmission of pressure from the forward body of gaseous fiuid to the rearward body of liquid fluid to permit the forward body of gaseous fluid to expand to drive the ram forward with consequent rearward retraction of the annular piston; and

means on the ram to engage the annular piston at the end of an initial portion of the forward stroke of the ram to terminate the retraction of the annular piston thereby to terminate the expansion of the forward gaseous body and to advance the annular piston with the ram over a final portion of the forward stroke of the ram.

2. A combination as set forth in claim 1 in which the rearward portion of the ram is formed with an enlargement to engage and drive the annular piston.

3. A combination as set forth in claim 2 in which the rear face of the annular piston is recessed to form a seat for the enlargement of the ram to provide a dashpot action when the enlargement approaches the annular piston.

4. A combination as set forth in claim 1 in which the part of the ram that is slidingly embraced by the annular piston is of reduced diameter to reduce the extent of retraction of the annular piston during the initial portion of the stroke of the ram.

5. A combination as set forth in claim 1, in which the cross-sectional area of the guide passage and the portion of the ram therein are smaller than the cross-sectional area of the forward compartment whereby the forward movement of the anular piston by the ram during the final portion of the forward stroke of the ram compresses the forward body of gaseous fluid to decelerate the ram and to restore energy for return movement of the ram.

6. A combination as set forth in claim 1 which includes:

a seat in the rear end of the rearward compartment for the rear end of the ram to isolate the rear end of the ram from the fluid pressure in the rearward compartment; and

means to terminate the isolation of the rear end of the ram to initiate a working stroke ofthe ram.

7. A combination as set forth in claim 6 in which the rearward portion of the ram that is embraced by the annular piston is smaller in cross section than the forward portion of the ram whereby the gaseous fluid in the forward compartment exerts a forward thrust on the forward portion of the ram; and

in which the rear end of the ram has an enlargement to seat in said seat, the enlargement being smaller in cross section than the rearward chamber but larger in cross section than the forward portion of the ram,

whereby when the enlargement is seated in the seat the fluid in the rearward chamber exerts a rearward thrust on the enlargement that is greater than said forward thrust on the forward portion of the ram whereby the thrust differential normally tends to keep the ram retracted in said seat.

8. In an impact apparatus of the character described,

the combination of:

a cylindrical structure to confine fluid under pressure, said structure having a forward longitudinal portion of a first diameter and a rearward longitudinal portion of a second larger diameter;

a ram having a forward portion slidingly mounted in said forward portion of the structure and a rearward end portion extending into said rearward portion of the structure,

the diameter of said rearward portion of the ram being less than said second diameter whereby fluid confined in the rearward portion of the structure may flow around the rear end of the ram to act on the rear end surface of the ram;

a floating annular piston sealingly and slidingly embracing the rearward portion of the ram and sealingly and slidingly contacting the inner circumferential surface of said rearward portion of the structure thereby cooperating with the ram to divide the interior of the structure into a rearward compartment and a forward compartment, the rearward compartment enclosing part of the rear portion of the ram including the rear end surface of the ram, the for- Ward compartment surrounding an intermediate portion of the ram;

a body of liquid in the rearward compartment;

21 body of compressed gaseous fluid in the forward compartment acting on the floating piston to place the body of liquid under pressure;

means in said rearward compartment to releasably seat the rear end of the ram to isolate the rear end face of the ram from the pressure of the liquid body;

means to unseat the rear end of the ram to give the liquid body access to the rear end face of the ram to drive the ram; and

cooperating means on the ram and the floating piston respectively for mutual engagement to limit the retraction of the floating piston relative to the ram whereby the stroke of the ram is divided into an initial portion wherein the gaseous body expands with rearward movement of the floating piston to act on the liquid body to drive the ram and a second portion wherein the ram carries the floating piston forward to compress the gaseous fluid to a degree determined by the difference between the first and second diameters to decelerate the ram and to store energy for return movement of the ram.

9. A combination as set forth in claim 8 in which said cooperating means on the ram and the floating piston respectively constitute dashpot means to cushion said mutual engagement.

10. In an impact apparatus, the combination of:

a structure forming a rearward chamber with a guide passage extending forward therefrom;

an impact ram having a forward impact portion slidingly mounted in the guide passage and a rearward portion extending into the rearward chamber, said rearward portion being of smaller cross-sectional area than the rearward chamber;

an annular piston slidingly mounted in the rearward chamber and slidingly embracing the ram to cooperate therewith to divide the chamber into a rearward compartment and a forward compartment;

a rearward body of liquid fluid in the rearward compartment to act on the rear end of the ram to drive the ram;

a forward body of compressed gaseous fluid in the forward compartment,

the annular piston being freely movable for transmission of pressure from the forward body of gaseous fluid to the rearward body of liquid fluid to permit the forward body of fluid to expand to drive the ram forward with consequent rearward retraction of the annular piston;

means on the ram to engage the annular piston at the end of an initial portion of the forward stroke of the ram to terminate the retraction of the annular piston thereby to terminate the expansion of the forward gaseous body and; to advance the annular piston with the ram over a final portion of the forward stroke of the ram,

the cross-sectional area of the guide passage being smaller than the cross-sectional area of the forward compartment whereby the forward movement of the annular piston by the ram during the final portion of the forward stroke of the ram compresses the forward body of gaseous fluid to decelerate the ram and to store energy for return movement of the ram;

a seat in the rearward compartment for the rear end of the ram to isolate the rear end of the ram from the fluid pressure in the rearward compartment until a working stroke of the ram is desired;

means to terminate the isolation of the rear end of the ram to initiate a working stroke of the ram; and

means to release liquid from the rearward compartment in response to excessive rise of pressure therein to prevent the creation of a destructive pressure therein when the ram is returned by expansion of the forward body of gaseous fluid.

11. A combination as set forth in claim in which said means to release liquid from the rearward compartment includes:

an auxiliary cylinder in communication with said seat;

an auxiliary piston in said auxiliary cylinder;

means placing the auxiliary cylinder in communication with said forward compartment to create pressure in the auxiliary cylinder against the rearward surface of the auxiliary piston; and

means to vent the space between the auxiliary piston and the seat whereby a pressure differential is normally created across the auxiliary piston to urge the auxiliary piston toward the seat.

12. In an impact apparatus, the combination of:

a cylindrical structure having a rearward longitudinal portion with a closed rear end and a forward longitudinal portion of smaller inside diameter than the rearward portion;

a ram in said structure having a leading end slidingly mounted in the forward longitudinal portion of the structure, said ram having a trailing end with a trailing end face in the rearward longitudinal portion of the structure,

the ram having an intermediate longitudinal portion smaller in diameter than the inside diameter of the rearward portion of the structure and forming with the rearward portion an annular space;

a floating annular piston in said annular space and dividing the interior of the structure into a rearward compartment at the closed end of the structure and a forward compartment;

a body of liquid in the rearward compartment;

a body of compressed gaseous fluid in the forward compartment;

a seat in the closed end of the rearward compartment to receive the trailing end of the ram to isolate the trailing end face of the ram from the liquid in the rearward compartment, sai-d seat being normally vented to keep the fluid pressure therein relatively low;

means operable to release liquid from said rearward compartment to permit the gaseous fluid in the forward compartment to retract the floating piston, the floating piston being constructed to engage the ram to retract the ram to place the trailing end of the ram in said seat;

means operable to introduce hydraulic fluid into the rearward compartment when the trailing end of the ram is seated, thereby to advance the floating piston to compress the body of gaseous fluid in the forward compartment to a desired degree; and

means to unseat the seated trailing end of the ram to expose the trailing end face of the ram to the prefsure of the liquid in the first annular chamber to cause the fluid pressure in the two compartments to drive the ram forward.

13. In an impact forming apparatus in which a first forming die is mounted on a normally stationary movable body and a ram makes impact against the movable body to drive the first forming die against a stationary second forming die, the improvement to facilitate retraction of the first die after a workpiece is formed by the two dies, comprising:

means confining a compressed body of gaseous fluid, said confining means including a surface united with the movable body to urge retraction of the movable body thereby to retract the first die from the second die to a retracted position after a forming operation; means normally holding the first die at a normal position advanced beyond said retracted position in opposition to the pressure of said body of gaseous fluid and in preparation for a forming operation, said holding means blocking retraction of the first die without blocking advance of the first die for a forming operation,

said holding means being releasable to permit the pressure of said body of gaseous fluid to retract the first die to said retracted position after a forming operation; and

means to restore the first die from its retracted position to its normal advanced position.

14. An improvement as set forth in claim 13 in which said restoring means is hydraulically actuated.

15. In an impact apparatus of the character described,

the combination of:

a cylindrical structure to confine fluid under pressure, said structure having a forward longitudinal portion of a first diameter and a rearward longitudinal portion of a second larger diameter:

a ram having a forward portion slidingly mounted in said forward portion of the structure and a rearward end portion extending into said rearward portion of the structure,

the diameter of said rearward portion of the ram being less than said second diameter whereby fluid confined in the rearward portion of the structure may flow around the rear end of the ram to act on the rear end surface of the ram;

a floating annular piston sealingly and slidingly embracing the rearward portion of the ram and sealingly and slidingly contacting the inner circumferential surface of said rearward portion of the structure thereby cooperating with the ram to divide the interior of; the structure into a rearward compartment and a forward compartment, the rearward compartment enclosing part of the rear portion of the ram including the rear end surface of the ram, the forward compartment surrounding an intermediate portion of the ram;

13 14 a body of liquid in the rearward compartment; vance of the floating piston relative to the ram and a body of compressed gaseous fluid in the forward comto cause the advancing floating piston to unseat the partment acting on the floating piston to place the rear end of the ram to give the liquid body access to body of liquid under pressure; the rear end face of the ram to initiate an operating means in said rearward compartment to releasably seat 5 stroke of the ram whereby an operating stroke of the rear end of the ram to isolate the rear end face the ram is initiated automatically by advance of the of the ram from the pressure of the liquid body; floating piston in response to the introduction of cooperating means on the ram and the floating piston liquid into the rearward compartment.

respectively for mutual engagement to limit the retraction of the floating piston relative to the ram 10 References Cited whereby the stroke of the ram is divided into an ini- UNITED STATES PATENTS tial portion wherein the gaseous body expands with rearward movement of the floating piston to act on 3 i the liquid body to drive the ram and a second por- 317O487 2/1965 5 5 'tion wherein the ram carries the floating piston for- 15 65 S ward to compress the gaseous fluid to a degree de- Z g 22 2 0 ar termined by the difference between the first and second diameters to decelerate the ram and to store energy for return movement of the ram; and CHARLES LANHAM P'lmary Exammer' cooperating means on the ram and the floating piston 20 G. P. CROSBY, Assistant Examiner.

respectively for mutual engagement to limit the ad- 

1. IN AN IMPACT APPARATUS, THE COMBINATION OF: A STRUCTURE FORMING A REARWARD CHAMBER WITH A GUIDE PASSAGE EXTENDING FORWARD THEREFROM; AN IMPACT RAM HAVING A FORWARD IMPACT PORTION SLIDINGLY MOUNTED IN THE GUIDE PASSAGE AND A REARWARD PORTION EXTENDING INTO THE REARWARD CHAMBER, SAID REARWARD PORTION BEING OF SMALLER CROSS-SECTIONAL AREA THAN THE REARWARD CHAMBER; AN ANNULAR PISTON SLIDINGLY MOUNTED IN THE REARWARD CHAMBER AND SLIDINGLY EMBRACING THE RAM TO COOPERATE THEREWITH TO DIVIDE THE CHAMBER INTO A REARWARD COMPARTMENT AND A FORWARD COMPARTMENT; A REARWARD BODY OF LIQUID FLUID IN THE REARWARD COMPARTMENT TO ACT ON THE REAR END OF THE RAM TO DRIVE THE RAM; A FORWARD BODY OF COMPRESSED GASEOUS FLUID IN THE FORWARD COMPARTMENT, THE ANNULAR PISTON BEING FREELY MOVABLE FOR TRANSMISSION OF PRESSURE FROM THE FORWARD BODY OF GASEOUS FLUID TO THE REARWARD BODY OF LIQUID FLUID TO PERMIT THE FORWARD BODY OF GASEOUS FLUID TO EXPAND TO DRIVE THE RAM FORWARD WITH CONSEQUENT REARWARD RETRACTION OF THE ANNULAR PISTON; AND MEANS ON THE RAM TO ENGAGE THE ANNULAR PISTON AT THE END OF AN INITIAL PORTION OF THE FORWARD STROKE OF THE RAM OF TERMINATE THE RETRACTION OF THE ANNULAR PISTON THEREBY TO TERMINATE THE EXPANSION OF THE FORWARD GASEOUS BODY AND TO ADVANCE THE ANNULAR PISTON WITH THE RAM OVER A FINAL PORTION OF THE FORWARD STROKE OF THE RAM. 